Why It Can Look Like Your Watch Has Stopped When You Glance At It (Even Though It Hasn't)

You may have noticed, during a long stint in a boring lecture or class, that when you glance at the clock, it sometimes seems as if the clock has stopped running. You stare in disbelief, wondering briefly if you’ve fallen into some sci-fi time warp, but then, to your relief, the clock starts advancing again. You might even have noticed the same phenomenon when you glance at your wristwatch – more often, when you’re wearing a quartz watch, and you may have wondered if time flows at different rates sometimes, or if you have some weird ability to briefly stop time.

You may have noticed, during a long stint in a boring lecture or class, that when you glance at the clock, it sometimes seems as if the clock has stopped running. You stare in disbelief, wondering briefly if you’ve fallen into some sci-fi time warp, but then, to your relief, the clock starts advancing again. You might even have noticed the same phenomenon when you glance at your wristwatch – more often, when you’re wearing a quartz watch, and you may have wondered if time flows at different rates sometimes, or if you have some weird ability to briefly stop time.

Photo: Petr Novák, Wikipedia

Neither is the right answer. What you’re actually experiencing is a phenomenon called “chronostasis” – the illusion of a temporary suspension of the passage of time. The key word here is “illusion.” You may not ever have thought about it, but when you rapidly move your eyes and look at something new in your field of vision, you don’t see any motion blur. This is because of so-called “saccadic masking” – your brain actually edits out the blur and fills in the blank with a prolonged image of whatever you’ve glanced at. This phenomenon of filling in a blank so there is no jarring discontinuity in perception happens in other ways as well; for instance, even with one eye shut, you can’t see your own blind spot (which is a gap in your visual field, due to the fact that in the back of the eye, where the optic nerve leaves, there are no retinal cells).

The overestimation of the duration of a stimulus can be up to 500 milliseconds. So no, when you’re bored out of your skull, and you glance at the clock, and time seems to have stopped, it hasn’t – but it sure looks that way for a half a second or so.